Weight Distribution Opinions

[achampagne]

So I am starting the design for the fuel system for my 87 ranger. I am going to put in a fuel cell into the truck to get better weight distribution, and to make room for the rear suspension shocks. My question is, which position for the new fuel cell would be best. The purpose of this truck is time attack and drift.
The first position would be behind the rear axle flush with the frame. Like below:

The perks of this is that it would keep the fuel cell low. However, it would bring the fuel cell further back than stock which would move the center of gravity closer to the rear.
The second position would be located right behind the cab. Like below:

The perks of this is it would keep the center of gravity closer to the center of the truck. However, because it has to sit high to make room for the drive shaft, it would raise the center of gravity a little higher compared to stock.
For anyone who has built a track specific car, what position would be better.

 

[Roert42]

Also consider that moving the center of gravity back may not be a bad thing, as trucks are traditionally front heavy already.

 

[sgtsandman]

@Maritime Drag Racing might have some helpful input for you. I think there is another person making a race truck Ranger build but I can't remember their name.

 

[1990RangerinSK]

@Maritime Drag Racing might have some helpful input for you. I think there is another person making a race truck Ranger build but I can't remember their name.

@RaceRanger97 maybe? I seem to remember somebody called Low Back (or Low Buck) Race Truck, but I can't seem to tag him.

 

[1990RangerinSK]

Also consider that moving the center of gravity back may not be a bad thing, as trucks are traditionally front heavy already.

Perhaps. OTOH, most cars are front heavy, too, unless they have a rear engine. It might be worth noting that while the box is light (maybe only a few hundred pounds, the engine is also a few hundred pounds. The rest of the 4,000 or so pound curb weight (likely 3k pounds) is in the frame and cab. I'd guess the cab is 2500 of that, and most of that weight is BEHIND the front axle, which distributes it between the front and rear axles.

I'd like to think that the engineers who designed the Ranger were aware of the weight distribution, and compensated for it in the design. Putting too much weight behind the rear axle might negate that compensation, which could cause unintended results.

 

[alwaysFlOoReD]

It's been a long time since I did the research for tank placement. In my case behind the rear axle made most sense. Centered in frame is better for many reasons that I forget right now, but you have to compromise most times.
Build thread for low buck race truck is in signature.

 

[1990RangerinSK]

It's been a long time since I did the research for tank placement. In my case behind the rear axle made most sense. Centered in frame is better for many reasons that I forget right now, but you have to compromise most times.
Build thread for low buck race truck is in signature.

Dagnabbit!! THAT'S where the Low Buck Race Truck came from that got stuck in my head! It's not somebody's userid, it's the NAME OF YOUR TRUCK! Ooops... One of these days this brain of mine is going to get me in SERIOUS trouble.

 

[Roert42]

can take a read through this thread, it’s mostly about front suspension modifications, but it’s mostly full of heavily modified street trucks.

It was started by @Yotaismygame

AJE Ranger K-Member Who's Done It!?

I don't think I've ever been more happy to spend 10k. After 15 months on order; the motor is finally here.

www.therangerstation.com

Even if it doesn’t help you much it’s a good ready anyway.

 

[Roert42]

I'd like to think that the engineers who designed the Ranger were aware of the weight distribution, and compensated for it in the design. Putting too much weight behind the rear axle might negate that compensation, which could cause unintended results.

Maybe/ maybe not. Depends on how much weight he strips off the truck too. Best thing to do is get a set of tire scales and balance the truck with the driver inside.

 

[lil_Blue_Ford]

Perhaps. OTOH, most cars are front heavy, too, unless they have a rear engine. It might be worth noting that while the box is light (maybe only a few hundred pounds, the engine is also a few hundred pounds. The rest of the 4,000 or so pound curb weight (likely 3k pounds) is in the frame and cab. I'd guess the cab is 2500 of that, and most of that weight is BEHIND the front axle, which distributes it between the front and rear axles.

I'd like to think that the engineers who designed the Ranger were aware of the weight distribution, and compensated for it in the design. Putting too much weight behind the rear axle might negate that compensation, which could cause unintended results.

Rangers (and really any truck intended for hauling) is nose heavy and tail light, otherwise loading the bed would cause problems. That’s always a hindrance for people building race trucks that they need to find ways to balance things better.

Of course, putting a fuel cell all the way back provides the most weight when it’s full of fuel and the least when it’s empty, so it will present a changing dynamic as you burn fuel. Putting it behind the cab will lessen the change because it’s closer to the heavy end.

 

[Yotaismygame]

I put my 15gal cell far back as possible, but that was just so I could fit a 3-link/panhard. I sunk it between the rails and used the tanks inc internal pump setup. If I had to do it over again I would just put it in the bed. Much easier to do. Plus I added a v8 with a turbo so the more weight I could get in the back the better.

 

[stmitch]

Behind the axle and low will keep the CoG near factory, but it also will improve front/rear weight distribution, improve traction, and make it easier to toss the rear out. It also means the bed can still be fully functional.

Behind the cab is basically the stock position, except higher. So you don't really improve F/R balance at all, you raise the CoG at the same time, and the bed becomes less useful. It's probably safer in the event of an accident though.

 

[superj]

tail heavy comes around quick at the autocross and drifting. you really have to spend some time learning where it loses traction because once it loses it, it goes all the way around.


ask any 911 drivers or air cooled vw guys. i put really wide tires on the back of my karmann ghia because of that

 

[stmitch]

tail heavy comes around quick at the autocross and drifting. you really have to spend some time learning where it loses traction because once it loses it, it goes all the way around.


ask any 911 drivers or air cooled vw guys. i put really wide tires on the back of my karmann ghia because of that

The thing that makes ACVWs or older 911s twitchy is not just that they have weight in the rear. It's that there's way more weight in the rear than the front. They're pretty unbalanced front/rear. Some quick searches say that an air cooled Beetle probably has a 40/60 front/rear weight balance. So the rear moves, and the steering gets light/ineffective at the same time.

A Ranger probably has the exact opposite weight balance starting with a 60/40 front/rear weight bias, and with a full tank behind the axle it might move to 55/45. It's still going to be nose heavy, even with the fuel cell all the way in the rear.

The Rolling Thunder project from a long time ago has some relevant info and weight balance theories for performance driving. They say the stock Ranger and the v8 swapped version of the same truck were 62F/38R weight balance:

 

[JoshT]

Also consider that moving the center of gravity back may not be a bad thing, as trucks are traditionally front heavy already.

First off in replying I want to clarify a few terms. Center of Gravity, moves up and down. Center of Balance moves forward and aft, side to side. There's also roll center, but that's a little complicated and it's been almost two decades since I messed with weight and balance in aviation maintenance school. You mostly hear about roll center in aviation, but it also has a place in automotive. It's not so easy to change in my mind and usually anti-roll bars are used to correct for it in automotive, but chassis and suspension setup play a huge part.

Truck's COG is high due to the height of much of the mass. Truck's COB is forward due to the forward weight bias. Roll center has a lot of factors, but everything you do to improve handling is going to improve roll center.

So I am starting the design for the fuel system for my 87 ranger. I am going to put in a fuel cell into the truck to get better weight distribution, and to make room for the rear suspension shocks. My question is, which position for the new fuel cell would be best. The purpose of this truck is time attack and drift.
The first position would be behind the rear axle flush with the frame. Like below:
View attachment 87552
The perks of this is that it would keep the fuel cell low. However, it would bring the fuel cell further back than stock which would move the center of gravity closer to the rear.
The second position would be located right behind the cab. Like below:
View attachment 87553
The perks of this is it would keep the center of gravity closer to the center of the truck. However, because it has to sit high to make room for the drive shaft, it would raise the center of gravity a little higher compared to stock.
For anyone who has built a track specific car, what position would be better.

Aft center, just do it. Select a baffled fuel cell (or one with foam) to keep the fuel from sloshing around affecting COB.

The ideal location would be middle of the frame in front of the rear axle. Unfortunately you need to put a driveshaft and probably some suspension bits there depending on what exactly you have planned.

Maybe you could rig up saddle tanks in front of the axle on either die of the driveshaft, but more difficult solution and once again you may need that space for suspension.

Placing above the driveshaft behind the in the center behind the cab would improve side/side weight balance but not front/rear balance. Moving it up on the frame (above driveshaft) will hurt the roll center, causing the truck to be more tippy. You might not notice it in general driving, but it will result in more side/side weight shift.

Behind the axle will keep weight low, which is good for COG. Moving weight to the rear will improve front/rear weight bias, helping with COB. The combination of those will help with roll center and should result in feeling better planted.

If you are trying to get real technical about it you might want to invest in a set of scales. Removing weight is the same as increasing power, and the better you get it dialed the better its going to respond to changes (to a point). Scales will help you shave weight and see how the balance responds to moving it around. Don;t forget to keep the driver weight in mind. You're probably going to want to add weight in the passenger seat area to counter balance the driver. If that can be done by relocating weight already existing and necessary in the vehicle, all the better.